Liner system for salt mine shafts

ABSTRACT

A mine shaft protective barrier includes an undercut in a wall surface of the mine shaft proximate to and below a water ingress ingress elevation. A fire-resistant material is applied within the undercut and downward along the wall surface below the to form a coating barrier that extends from the undercut downward along the mine shaft such that water entering the wall surface at the ingress location tends to flow downward into contact with and along an inward facing surface of the coating barrier so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the ingress location.

CROSS-REFERENCES

This application claims the benefit of U.S. Provisional Application Ser. No. 62/020,047, filed Jul. 2, 2014, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

This application relates generally to systems for sealing and/or protecting walls in mines, tunnels and other environments and, more particularly, to a sprayable system that is applied to provide such protection in salt mine shafts.

SUMMARY

In one aspect, a method of rehabilitating a wall surface of a salt mine shaft involved: (a) identifying an ingress location along a height of the wall surface at which water passes through the wall surface into the shaft; (b) forming a recess or undercut in the wall surface below the identified elevation; and (c) utilizing a plural component spray process to apply a fire-resistant material, in the form of a first polyurethane or polyurea compound, into the recess or undercut and along the wall surface below the recess or undercut forming a coating barrier that extends from the recess or undercut downward along the mine shaft such that water entering the wall surface at the ingress location tends to flow downward into contact with and along an inward facing surface of the coating barrier so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the ingress location.

In another aspect, a mine shaft protective barrier includes an undercut in a wall surface of the mine shaft proximate to and below a water ingress ingress elevation. A fire-resistant material is applied within the undercut and downward along the wall surface below the to form a coating barrier that extends from the undercut downward along the mine shaft such that water entering the wall surface at the ingress location tends to flow downward into contact with and along an inward facing surface of the coating barrier so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the ingress location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic cross-section of a sale mine shaft; and

FIG. 2 is a schematic partial cross-section of the liner system in such salt mine shaft.

DESCRIPTION

FIG. 1 shows a schematic cross-section along a vertical plane passing through salt mine shaft 10. The wall surface 12 of the shaft extends generally vertically, although variations are possible. A ground seam 14 represents a location at which water tends to migrate into the mine shaft 10 and then flow downward along the wall surface 12, which can degrade the wall surface, particularly where the mine shaft is formed in a salt material. This problematic issue is addressed in the following manner.

As seen in FIG. 2, a recess or undercut 16 is formed in the wall surface below the seam 14. By way of example, a depth of the recess or undercut may be on the order of three to six inches deep and about three to six inches high (e.g., about 4 inches deep and about 4 inches high). The recess or undercut may be generally of a continuous annular configuration in the wall surface. A fire-resistant material (e.g., in the form of a polyurethane or polyurea compound) is applied (e.g., using a plural component spray process) into the recess or undercut 16, as well as along the wall surface 12 below the recess or undercut 16, thereby forming a coating barrier 18 that extends from the recess or undercut 16 downward along the mine shaft 10. The barrier 18 then operates such that water entering the wall surface 12 at the seam 14 tends to flow downward into contact with and along an inward facing surface 20 of the coating barrier 18 so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the seam 14.

To increase the stability of the mine shaft 10, voids 22 or recessed pockets formed by the coating barrier (e.g., resulting from a configuration of the wall surface prior to spraying the barrier 18) may be identified. A structural foam material 24 (e.g., in the form of another polyurethane or polyurea compound) is then applied (e.g., using a plural component spray process) into the void recesses. The fire-resistant material is then applied over the structural foam material in each void recess, as per 26. The fire-resistant material 26 is applied so as to bond with coating barrier 18 such that the structural foam material 24 is completely encased in the fire-resistant material.

In one embodiment, the structural foam material includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant and (iii) a foaming agent, and the fire resistant material includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant.

In one implementation of the foregoing embodiment, the isocyanate of the structural foam material is 4,4-diphenylmethane diisocyanate, and the isocyanate of the fire resistant material is selected from the group consisting of isophorone diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

As used herein, the term plural component processing technique means blending two or more chemicals together in a specific or varying ratio with either direct impingement equipment, equipment utilizing a static mixer assembly to mix/bled the chemicals or by mixing in an open container by hand or by other mechanical mixing method to produce material that cures to some degree. In the primary embodiment, an impingement mix spray process is used.

It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. For example, in mine shafts including equipment structure below the seams (e.g., such as one or more elevator rails running vertically along the mine shaft), a spray of the fire-resistant material could be applied to such equipment structure. 

What is claimed is:
 1. A method of rehabilitating a wall surface of a salt mine shaft, the method comprising, comprising: (a) identifying an ingress location along a height of the wall surface at which water passes through the wall surface into the shaft; (b) forming a recess or undercut in the wall surface below the identified ingress elevation; (c) utilizing a plural component spray process to apply a fire-resistant material, in the form of a first polyurethane or polyurea compound, into the recess or undercut and along the wall surface below the recess or undercut forming a coating barrier that extends from the recess or undercut downward along the mine shaft such that water entering the wall surface at the ingress location tends to flow downward into contact with and along an inward facing surface of the coating barrier so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the ingress location.
 2. The method of claim 1, further including: (d) identifying a void recess in a configuration of the coating barrier resulting from a configuration of the wall surface; (e) utilizing a plural component spray process to apply a structural foam material, in the form of a second polyurethane or polyurea compound, into the void recess; (f) utilizing a plural component spray process to apply the fire-resistant material over the structural foam material.
 3. The method of claim 2 wherein steps (d), (e) and (f) are performed multiple times corresponding to multiple void recesses.
 4. The method of claim 2 wherein in step (f) the fire-resistant material is applied so as to bond with the coating barrier of step (c) such that the structural foam material is completely encased in the fire-resistant material.
 5. The method of claim 1 wherein the fire-resistant material is applied in multiple passes.
 6. The method of claim 1 wherein the fire-resistant material is sprayed onto the wall from a dispensing device aperture that is at least ten feet from the wall surface.
 7. The method of claim 1 wherein the fire-resistant material is sprayed onto the wall from a dispensing device aperture that is at least fifteen feet from the wall surface.
 8. The method of claim 2 wherein: the fire-resistant material includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant, but not including any foaming agent; and the structural foam material includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant and (iii) a foaming agent to create a foaming characteristic.
 9. The method of claim 8 wherein: the isocyanate of the structural foam material is 4,4-diphenylmethane diisocyanate; the isocyanate of the fire resistant material is selected from the group consisting of isophorone diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.
 10. The method of claim 1 wherein the wall surface comprises a salt material.
 11. A mine shaft protective barrier, comprising: an undercut in a wall surface of the mine shaft proximate to and below a water ingress ingress elevation; a fire-resistant material applied within the undercut and downward along the wall surface below the to form a coating barrier that extends from the undercut downward along the mine shaft such that water entering the wall surface at the ingress location tends to flow downward into contact with and along an inward facing surface of the coating barrier so as to inhibit such water from flowing in contact with and degrading the wall surface of the mine shaft below the ingress location.
 12. The mine shaft protective barrier of claim 11, further comprising: multiple recessed pockets formed by the fire-resistant material, each recessed pocket having a structural foam material, in the form of a second polyurethane or polyurea compound, applied therein, and an additional application of the fire-resistant material over the structural foam material.
 13. The mine shaft protective barrier of claim 12 wherein, for each recessed pocket, the fire-resistant material completely encases of the structural foam material in the recessed pocket. 